​​​​​​​Release of Official Maps of Revised Earthquake Fault Zones

      June 15, 2017

​​Three revised Official Maps of Alquist-Priolo Earthquake Fault Zones were released on June 15, 2017 by the California Geological Survey (CGS).  Areas covered are within Los Angeles County and affect the cities of Arcadia, Los Angeles, Monrovia, Pasadena, San Marino, and South Pasadena. These maps are released under the authority of the Alquist-Priolo Earthquake Fault Zoning (AP) Act that was passed following the 1971 San Fernando earthquake.  The AP​ Act​​ is a state law designed to reduce the hazard from surface fault rupture during an earthquake.  Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. ​

These revised maps show the location of AP Earthquake Fault Zones (EFZ) and Seismic Hazard Zones (SHZ), if evaluated, and are collectively referred to as Earthquake Zones of Required Investigation.  An electronic version of the zone maps, referred to as a GeoPDF file, can be viewed using Adobe Acrobat Reader.  This GeoPDF file consists of multiple layers and gives the user greater flexibility in viewing and displaying the maps. 

Digital Geographic Information System (GIS) files for both AP Earthquake Fault Zones and Seismic Hazard Zones released by CGS are considered the “Official Maps.”  GIS files for EFZ and SHZ, as well as GeoPDF maps and associated Fault Evaluation Report (FER) pdf files, can be downloaded from the table below for the June 15 release.​


Fault Evaluation Report 7.5 Minute Quadrangles GIS Data
FER 260  Los Angeles

Los Angeles​

FER 264  El Monte​
Mount Wilson

El Monte
Mount Wilson​